Amy,
I don’t know how much time you have (read: desperate), but you may not have to do a Clean Install. As you know, you’d have to start from scratch with all of your files and preferences. Personally, I’d rather have a root canal.
If you can’t easily install the new software, it sounds like some of your system files are corrupted. You may be able to fix them by booting from one of your Mac OS Installation Disks and running “Disk First Aid”. DFA will repair (or at least report) on a multitude of problems.
And, if you are having problems with your administrator or user passwords, there is a way to reset them from the Installation Disks, too. I have never had to do that, so I cannot give you a step-by-step, but there is a way. Instructions are probably in the “Help” menu on the Install DVD somewhere.
Also, if you don’t already have a copy, I might suggest you grab a copy of Alsoft’s <u>Disk Warrior</u>. Norton’s <u>Disk Doctor</u>, which I had been using for years with OS 9, has turned into “Disk Mortician” when OS X was released.
Don’t use Norton Utilities to try to fix anything on OS X! NDD corrupts directory files beyond repair! It got so bad for me, when I booted, I was taken directly into the Terminal Mode – which was so confusing to me that I couldn’t even find my way out of it.
Try running “Disk First Aid” from the Installation Disk before you do anything else.